Unformatted text preview: he deflections in the SP curve to be rounded off and to reduce the amplitude of thin beds. • A larger wellbore will cause, like a mud filtrate invasion, the deflections on the SP curve to be rounded off and decrease the amplitude opposite thin beds, while a smaller diameter wellbore has the opposite effect. 61 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration Resistivity Tools:
Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current. The log must run in holes containing electrically conductive mud or water. 1-Electrode tools: Modern Resistivity Log: Laterologs: (LL) It is a type of modern electrodes which have a number of electrodes. • LL3 has 3 current emitting electrodes (vertical resolution is 1ft). • LL7 has 7 current emitting electrodes (vertical resolution is 3ft). • LL8 is similar to the LL7, but has the current return electrode (vertical resolution is 1ft). Dual Laterologs: (DLL) It is the latest version of the laterolog. As its name implies, it is a combination of two tools, and can be run in a deep penetration (LLd) and shallow penetration (LLs) mode. These are now commonly run simultaneously and together with an additional very shallow penetration device. The tool has 9 electrodes. Both modes of the dual laterolog have a bed resolution of 2 feet. The resistivity readings from this tool can and should be corrected for borehole effects and thin beds, and invasion corrections can be applied. LL3 LL7 SFL The dual laterolog is equipped with centralizes to reduce the borehole effect on the LLs. A micro resistivity device, usually the MSFL, is mounted on one of the four pads of the lower of the two centralists. NOTE: Separation of the LLs and LLd from each other and from the MSFL is indicating the presence of a permeable formation with hydrocarbons. Sphe...
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This note was uploaded on 01/05/2011 for the course GEOL 1 taught by Professor Jenniferalford during the Spring '10 term at Indian Institute of Technology, Roorkee.
- Spring '10